Distribution type tactile sensor

ABSTRACT

A distribution type tactile sensor, which comprises a plurality of electrodes provided in pairs at respective pressure sensing points on a pressure sensitive conductive rubber sheet capable of changing the electrical resistance responsive to compressive forces, and a rectifier element provided to respective electrodes for rectifying the current flowing across each pair of electrodes through the rubber sheet, the electrodes being divided into groups each comprising electrodes arranged in a line for respective polarities of the electrodes, electrodes in respective electrode groups being parallel connected to one another through electrode leads, and directions of the division of electrode groups divided for respective polarities being crossed with one another at respective pressure sensing points.

DESCRIPTION

1. Art Field

The present invention relates to a device for detecting contactpressures distributed in a certain breadth of area, using a pressuresensitive conductive rubber capable of changing the electricalresistance in response to compression forces, and displaying the resultof detection on a display device in the form of an image or a drawingfigure.

2. Background Art

To let a robot or the like handle objects, one practice is to provide asensor comparable to a tactile organ on the surface of a hand of therobot or the like against which the objects to be handled are contactedso that the objects can be held or gripped with an appropriate degree offorce or wherein their configurations can be recognized by the sensor.Conventionally, materials such as semiconductors, ceramics, organicmaterial, optical fibers and so forth are known to be useful for sensorelements. However, the known measurement systems made with use of suchmaterials have problems with their flexibility and/or involvedifficulties such that they cannot be made compact, they fail to providesufficient resolving power for analyzing respective forces, distributedover an area and/or they are not economically feasible. Thus, it is thepresent status of art that a satisfactory measurement system has not yetbeen provided.

With the above status of the art in mind, the inventors of the presentinvention have previously invented a distribution type tactile sensorwhich makes use, for the sensor element, of a rubber which normally isan insulator but which, when subjected to deformation by an appliedforce, changes its electrical resistance in response to a change in theamount of the deformation (this rubber will hereinafter be referred toas pressure sensitive conductive rubber). This sensor can determine theforces applied on various contact points of the sensor at which thesensor is contacted with an object. This invention formed the subjectmatter for a patent application filed in Japan under the patentapplication No. 60-219245.

The above tactile sensor is of an arrangement in which electrodes areprovided in pairs at each measurement point for the measurement ofcompression forces on a thin sheet-type pressure sensitive conductiverubber, and by which the forces applied at the measurement points aredetected as changes in the electrical resistance of the conductiverubber at such measurement points. This tactile sensor may be applliedto an object holding surface of, for example, a robot and utilized as atactile detecting sensor. Electrodes may be provided in a sufficientnumber as required for the holding of an object, and the number ofelectrodes to be provided is, for example, on the order of 16 to 25.

The invention disclosed in the above cited Japanese patent applicationmakes a combined use of a thin layer of a flexible pressure sensitiveconductive rubber and electrode leads, and thereby dispenses with theneed of providing a sensor at each of the measurement points, thusmaking it possible to provide a sensor device having a function closelyresembling the function of human hands. Thus, the touch or tactilesensor of the invention referred to above can be widely utilized, notonly in controlling the force of holding or gripping depending on thestrength, the weight, the configuration and so forth of an object to behandled and/or depending on the particular purpose of the handling, butalso in distinguishing shapes or configurations of objects and detectingslip or slide, by contacting or touching.

In view of the above, it will be appreciated that by using a sensordevice having a number of touch or contact detecting points closelyarranged in longitudinal and transverse directions (hereinafter referredto as distribution type tactile sensor), it is possible to display theconfiguration of the object against which the sensor device iscontacted, and the distribution of the contact pressures on the object,in the form of an image or a drawing figure. An attempt made in order torealize this possibility is reported in the Report No. 4016 by Ishikawaet al of Seihin Kagaku Kenkyusho (Industrial Products ResearchInstitute), entitled "Pressure Distribution Sensor Emitting VideoSignals", entered in the proceedings of the 28th Japan Joint AutomaticControl Congeference under the Society of Instrument and ControlEngineers (Nov. 5 to 7, 1986).

The above Report carries a brief disclosure of the technique accordingto which, now that it is necessary to provide a number of electrodes inorder to tell the configuration of an object by means of contactpressures with which the sensor contacts the object, there are provided4096 electrodes arranged in 64 lines or rows in each of the longitudinaland transverse directions, and an image of the palm of a hand isdisplayed on a television tube, utilizing circuits detecting electricalresistance of a pressure sensitive conductive rubber on respectiveelectrodes.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a sensing circuit in orfor a distribution type tactile sensor provided with a number, forexample, 4000 or more, of small electrodes for tactile sensing anobject. The contact pressures at which the object is contacted by thesensor can be detected to display the configuration of the object in theform of an image or a drawing figure. The sensing circuit of the presentinvention is in that in comparison to the existing comparable circuits,it can detect tactile signals at respective electrodes at a higheraccuracy and a higher speed and can reduce the required number of leadsor wires and the consumption of power.

Another object of the invention is to provide an image display systemfor displaying images and/or drawing figures, using a distribution typetactile sensor made with use of the above sensing circuit.

Yet another object of the invention is to provide various tactilesensing parts having a tactile sensing surface, adapted to particularpurposes of detection or measurement.

The distribution type tactile sensor for attaining the above objectsaccording to the present invention makes use of a sensing circuit whichis characterized in that electrodes are provided in parts at respectivepoints for measurement of compression forces applied to a pressuresensitive conductive rubber sheet capable of changing the electricalresistance responsive to a change in the compression force, a rectifierelement being provided to respective electrodes for rectifying thecurrent flowing across each pair of electrodes through the rubber sheet,the electrodes being divided into groups each comprising electrodesarranged in a line or row for respective polarities of the electrodes,electrodes in respective electrode groups being parallel connected toone another through electrode leads, and directions of the division ofelectrode groups divided for respective polarities being crossed witheach other at respective points for the measurement of compressionforces.

According to the invention, it is possible to provide an image or figuredisplay system by processing by a computer the sensed tactile signalsoutputted from the distribution type tactile sensor made with use of theabove sensing circuit, and then by displaying the processed signals onfor example a television tube.

Electrodes can be formed by means of attaching onto a surface of apressure sensitive conductive rubber any of such as rare metal foils,aluminium foils and other metal foils the surface of which is treatedfor rust prevention, or by laminating on the rubber an insulating filmof a synthetic resin having a flexibility and a high strength, forexample polyethylene terephthalate, after this film is applied with aprinted wiring and its surface is plated with gold or otherwise coatedwith any of carbon black, graphite and so forth.

The pressure sensitive conductive rubber for use for or in the presentinvention may be any of known pressure sensitive conductive rubberscomprising conductive particles such as carbon particles dispersed inrubber or an elastomer such as silicone rubber for example. Althoughthis conductive rubber is normally used in the form of a sheet, whichmay be cut into pieces of the prescribed size, it is also possible touse a rubber in the form of a coating material, which may be applied onelectrodes for example by coating and may then be solidified thereon.

The above described distribution type tactile sensor according to thepresent invention and the image display system made with use of such atactile sensor can be applied to a variety of uses. For example, a usemay be made for measuring the weight applied on the sole of a foot orsoles of feet to then operate a diagnosis and/or to determine a guidancefor rehabilitation, of a handicapped person. Also, in the carrying outof research work and/or designing activity in the field of human-factorsengineering, a use may be possibly made for obtaining data for thedesigning of sporting shoes and other shoes or the designing of officechairs by investigating the relationship between the manner in which awearer of shoes walks and the load distribution over various portions ofthe shoes, or the relationship between the sitting posture of a user ofa chair and the distribution of loads over various portions of thechair. A use may also be made in or for industrial robots whichautomatically classify parts and members respectively having acharacteristic shape or configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 show a view, taken for illustration of a sensing circuit in adistribution type tactile sensor of the prior art, used in a robot'shand;

FIG. 2 is a view, taken for a brief illustration of a sensing circuit ofa distribution type tactile sensor in the prior art, used in an imagedisplay system;

FIG. 3 shows a perspective view of electrodes used in the circuit ofFIG. 1;

FIG. 4 is a circuit diagram, taken for illustration of a problem withthe circuit of FIG. 1;

FIG. 5 is a view, taken for illustration of the reason for thegeneration of a stray current in the circuit of FIG. 4;

FIG. 6 is a perspective partial view, showing the structure of a sensingpart in a distribution type tactile sensor according to an embodiment ofthe present invention, shown in a disassembled condition;

FIG. 7 shows a vertical sectional view through FIG. 6;

FIG. 8 is a view, taken for illustration of the reason for why the straycurrent is not generated in the sensing part shown in FIG. 6;

FIG. 9 shows a view, taken for illustration of electrodes in adistribution type tactile sensor according to another embodiment of thepresent invention;

FIG. 10 is a partly broken-away perspective view, showing thedistribution type tactile sensor incorporating the electrodes shown inFIG. 9;

FIG. 11 shows a sectional view taken on the line XI--XI in FIG. 9;

FIG. 12 shows switching circuits in the contact sensing circuit;

FIGS 12A-12C show separate parts of FIG. 12;

FIG. 13 shows a sectional view of essential portions of the switchingcircuits of FIG. 12;

FIG. 14 is a block diagram of a picture display system;

FIG. 15 is also a block diagram but shows an imaging unit in the imagedisplay system of FIG. 14;

FIG. 16 is a view, showing a use condition of the image display systemof FIG. 14;

FIG. 17 depicts a block diagram of a control system used in a robot'shand;

FIG. 18 is a partly broken-away perspective view, showing a plate typesensor device adapted to have mounted to thereon a human body or anobject;

FIG. 19 shows a pattern of electrodes for use in or for the distributiontype tactile sensor device shown in FIG. 18;

FIG. 20 shows a schematic view of a sensing circuit in or for adistribution type tactile sensor adapted to curved surfaces;

FIG. 21 shows a partly broken-away perspective view of an example ofunit sensors for use in or for the distribution type tactile sensorshown in FIG. 20;

FIG. 22 is a perspective view, showing an example of use of thedistribution type tactile sensor of FIG. 20;

FIG. 23 shows a partial plan view of an example of electrode leads in orfor the tactile sensor of FIG. 20;

FIG. 24 shows a stretched condition of the electrode lead of FIG. 23;

FIG. 25 shows a modified example of the unit sensor of FIG. 21;

FIG. 26 shows a connector portion in FIG. 25;

FIG. 27 is a partly broken-away perspective view, showing anothermodified example of the unit sensor of FIG. 21;

FIG. 28 shows a sectional view, taken on the line IIXXX--IIXXX in FIG.27;

FIG. 29 shows a perspective view of a shoe incorporating a distributiontype tactile sensor;

FIG. 30 is a partly broken-away perspective view of a unit sensor foruse in or for the tactile sensor of FIG. 29;

FIG. 31 is a plan view, showing essential portions in FIG. 30, in anenlarged scale;

FIG. 32 is a sectional view, taken on the line XXXII--XXXII in FIG. 31;

FIG. 33 shows a sectional view of an adaptor for increasing the sensingdensity; and

FIG. 34 is a sectional view of an adaptor for sensing convex and/orconcave surfaces in a recessed part or portion of an object.

BEST MODE OF CARRYING OUT THE INVENTION

Now, detailed descriptions will be successively provided of a tactile ortouch sensing circuit in or for the distribution type tactile sensorsaccording to the present invention (in what will follow, the sensorswill be referred to simply as tactile sensors unless misunderstanding islikely), a picture display system made with use of one of the tactilesensors utilizing the tactile sensing circuit, material structures andmethods of use of touch sensors respectively adapted to a particularuse, in the mentioned order.

FIG. 1 is a view, taken for illustration of circuits used in theelectrode part according to the invention disclosed in the beforereferred-to Japanese patent application No. 60-219245, in which thedistribution type tactile sensor (touch sensor) indicated at 1, which isprovided in a robot's hand (not shown) comprises 16 electrodes Eij (i,j=0˜4). Four electrodes on the output side (hereinafter shown by Eo) areattached to each of four parallel arranged output electrode leads 2₀ to2₃ and disposed on a front surface of a sheet-type pressure sensitiveconductive rubber 3, and on the other, backside surface of the rubber 3,four feed electrode leads 4₀ to 4₃ having feed-side electrodes Ep (notshown) attached thereto at the points corresponding to the locations ofthe electrodes Eo are so disposed as to cross the electrode leads 2₀ to2₃.

When a robot's hand having the above tactile sensor 1 is contactedagainst an object to be held by the robot's hand, a contact pressure isapplied to the pressure sensitive conductive rubber 3 and its electricalresistance undergoes a lowering, corresponding to which a current flowtakes place through electrodes Eij. Therefore, for example by connectingthe electrode lead 4₀ to a power source and by taking the currentsuccessively from each of the electrode leads 2₀ to 2₃, it is possibleto detect the contact pressure at each of the locations at which the 16electrodes Eij are provided. Accordingly, it is possible to control to acertain value the forces applied at various portions of the object beinggripped or otherwise held by the robot's hand, so that the robot's handcan safely hold various objects which cannot stand a strong forceapplication, such as eggs for example.

For the sensing of forces for purposes like that described above,generally it is not required to provide a very large number of sensingpoints, but if such sensing is for the purpose of detecting a shape orconfiguration of an object by a tactile sensor, as in the before citedtechnical Report by Ishikawa et al, it is necessary to considerablyincrease the number of the sensing points.

Now, with reference to FIGS. 2 and 3, a brief explanation will be giventhe distribution type tactile sensor according to the prior art madepublic by the above referred-to technical Report by Ishikawa et al.

In FIG. 2, the distribution type tactile sensor 1 comprises pairs ofelectrodes Eij (i=0 . . . 8 m˜8 m+7 . . . 63, j=0 . . . n-1, n, n+1 . .. 63; 4096 electrodes in total), which are disposed on a backside of apressure sensitive conductive rubber (not shown) and to which respectiveswitches Sij comprising FET, a resistance and a diode (i=0 . . . 8 m˜8m+7 . . . 63; j=0 . . . n-1, n, n+1 . . . 63; 4096 switches in total)are connected by electrode leads 2.

As shown in FIG. 3, the electrodes Eij comprise a square electrodehaving a side length of about 5 mm, in which an electrode Ep and anelectrode Eo shaped in the form of comb teeth are assembled in a meshingarrangement having a prescribed space therebetween. Electrodes Ep on theone hand and electrodes Eo on the other hand make up electrodes forconnection to a power source side and electrodes for connection to anoutput side, respectively. Further, on (the load bearing side of) theelectrodes Eij, the pressure sensitive conductive rubber 3 is placed.Although this rubber 3 is shown in FIG. 3 to be of a same size as theelectrode, usually the rubber 3 is in the form of a sheet, on which allthe electrodes Eij are attached.

In the tactile sensor 1, it is necessary to mount 4000 or more switches,as stated above, on a square sensor board having a side length of about32 cm, and to arrange electrode leads 4 for connecting all electrodes Epto a power source above the switches. Accordingly, a problem is posedthat the wiring cannot be performed with high efficiency. In view ofthis, and in order to miniaturize switches and build them in the touchsensor 1 so as to facilitate the wiring operation and also to reduce theoverall size of the device, in the case of the prior art exampleillustrated in FIG. 1, it has been proposed that switching circuits madewith use of FET's for the switching elements are collectively formed ona single switch board to provide a hybrid IC of 1×8 cells and of a pinpitch of 1.26 mm, which is disposed on a backside of the touch sensor 1.

However, in the case of the sensing circuits of FIG. 2, it is necessaryto arrange 4096 electrode leads 2 for connecting together a sensor boardprovided with all electrodes Eij and a switch board provided with allswitches Sij at a spacing of about 5 mm and, in addition, connectelectrode leads 4 above the electrode leads 2 (FIG. 2). In this case,according to the above described prior art, a problem is met in that thewiring operation and the assembling of the device can only be performedat an extremely low operation efficiency.

In addition, according to the above described prior art, the switchboard has to be arranged on the backside of the tactile sensor 1 in acondition in which a great number of electrode leads 2 projecttherefrom, so that no means is made available for supporting the touchsensor 1 on the backside thereof. A further problem is posed in that inorder to effect a reinforcement, it is indispensable that the sensorboard itself to be very stiff, whereby it becomes difficult to reducethe thickness and the weight of the device.

It may possibly be made to apply the circuit of FIG. 1 to the sensingcircuit of the prior art shown in FIG. 2 to effectively reduce thenumber of the output leads for the respective electrodes. It isprovided, however, that unless a compensating circuit is provided, thecircuit of FIG. 1 cannot operate to display the shape or configurationof an object as described below. The reasons for this will be describedwith reference to FIGS. 4 and 5. Further, FIG. 5 shows an equivalentcircuit diagram, in which respective resistances R show equivalentresistances with the current flowing in a minimum flow path in thepressure sensitive conductive rubber.

For avoiding complexity in the description, in FIGS. 4 and 5 electrodeleads are shown to simply comprise the electrode leads 4₁ and 4₂ of FIG.1 on the pressure bearing side and the electrode leads 2₁ and 2₂ of FIG.1 on the backside, and the sensing points, namely the intersections ofthe leads, are shown to simply comprise P₁₁, P₁₂, P₂₁ and Q. Forpurposes of explanation, it may be tentatively supposed that whilerespective points P are in contact with an object and are exerting acontact pressure, the point Q is not in contact with the object and thatthe electrical resistance at the point Q is to be determined.

Electrical resistances between intersections of electrode leads 2 and 4are shown by R₁₁, R₁₂, R₂₁ and R₂₂ =∞ (∞ denotes that the electricalresistance of the rubber corresponds to that of an insulator). Now, asshown in FIG. 5, a voltage E may be impressed across electrode leads 2₂and 4₂, wherein, although no current flow actually takes place acrossthe resistance R₂₂, a stray current I [=E/(R₂₁ +R₁₁ +R₁₂ ] flows througha stray current circuit from the resistance R₂₁ to the resistance R₁₁and further to the resistance R₁₂ (R₂₁ →R₁₁ →R₁₂), whereby it iserroneously determined that a force is applied at the point Q.

Actual tactile sensors have a number of sensing points, for example 8×8or more, and it is a problem with them that due to the stray current, itis impossible to detect accurate electrical resistance values.

As a consequence, conventional tactile or touch sensors may exhibit asatisfactory function wherein a relatively large space can be providedbetween sensing points or wherein the required conditions for thesensing is relatively not severe, but they cannot provide a tactilesensor having a relatively high power of resolution or analysis and anaccordingly high operation efficiency.

Now, with reference to FIGS. 6 and 7, a description will be provided ofthe arrangement of the sensing part in the distribution type tactilesensors according to the present invention.

FIG. 6 is a partial perspective view, showing essential portions of an8×8 matrix distribution type tactile sensor according to the presentinvention, in a disassembled condition. As shown, on the pressurebearing side of the pressure sensitive conductive rubber 3, there issuperposed a printed circuit plate 6 having a printed wiring ofelectrode leads 4 and feed-side electrodes Ep. Electrode leads 4 areshown by broken lines to show that they are printed on the side of theplate 6 facing the pressure sensitive conductive rubber 3. Electrodesforming parts of the electrode leads 4 are provided with the electrodesEp coated with a conductive coating material such as carbon black andgraphite, and the surface of the plate 6 is made rust preventive.

On the other, or the backside, surface of the pressure sensitiveconductive rubber 3, a printed circuit plate 8 is disposed, which isprinted, on a front-side surface, with output-side electrodes Eo in an8×8 matrix arrangement and, on the backside, with electrode leads 2. Theelectrode leads 2 and 4 are arranged to cross one another (in theillustrated embodiment, they cross at right angles). Electrodes Eo andleads 2 are connected together by diodes D.

FIG. 7 illustrates in section details of the wiring and connectiontogether of the diodes D and the electrodes Eo. As stated above, inactuality the electrodes Eo and the diodes D are provided on afront-side and a backside surfaces of the printed circuit plate 8.

As can be seen from the foregoing description, there are 8×8 sensingpoints in the sensing part of the tactile sensor according to thepresent invention, and these sensing points are divided into 8 groups,polarity by polarity. On each of the 8 electrode leads 2, 8 electrodesEo are connected in a linear arrangement, and lines of electrodes Eo areparallel arranged. Similarly, 8 electrodes Ep are connected in a lineararrangement on each of the 8 electrode leads 4, and lines of electrodesEp are parallel arranged.

The tactile sensor 1 according to FIGS. 6 and 7 does not produce thestray current described above in relation to FIG. 5, and can thereforeexhibit a drastically improved sensing accuracy. This will be nowdescribed with reference, for comparison FIG. 8, which corresponds topurposes, with prior art FIG. 5.

As can be seen from a comparison between FIG. 5 and FIG. 8, a diode D inthe tactile sensor 1 in FIG. 8 can prevent the stray current tending toflow through R₁₁, so that in this tactile sensor 1, a stray currentcircuit of R₂₁ →R₁₁ →R₁₂ is not formed. Therefore, for example where acontact force is applied at each of R₁₁, R₁₂ and R₂₁ but not at R₂₂, avoltage may be applied to the electrode lead 4₂ and current may be takenfrom the electrode lead 2₂, however, no output current will be producedas opposed to the before considered case of the prior art. That is tosay, using the circuit shown in FIGS. 6 and 7, it is possible toaccurately detect the current flowing across the electrodes Eij at theintersections of electrode leads 4 connected to a power source and theelectrode leads 2 for taking out the current.

FIG. 9 shows a perspective view of electrodes used in another embodimentof the tactile sensor according to the present invention, FIG. 10 beinga perspective view of a tactile sensor incorporating the electrodesshown in FIG. 9, and FIG. 11 being a sectional view, taken on the lineXI--XI in FIG. 9.

Similar to the electrodes shown in FIG. 3 (prior art), the electrodesshown in FIG. 9 comprise square comb-tooth shaped electrodes, which areprovided on just one of the two surfaces of a pressure sensitiveconductive rubber.

Electrodes Eo and Ep, and electrode leads 2 and 4, are printed on aprinted circuit plate shown at 17 in FIGS. 10 and 11, and the electrodeparts are formed by plating with gold. Electrodes Eo and electrodes Ep,each of which takes a comb-like shape, are assembled in a meshingarrangement with the prescribed gaps g maintained as shown. ElectrodesEp and leads 4 are integrally formed.

Electrodes Ep are connected to leads 2 printed on the other side surfaceof the printed circuit plate 6 through diodes D which form rectifierelements according to the present invention. As best seen from FIG. 11,taps t applied in thorugh-holes h formed in the printed circuit plate 6and electrode leads 2 are connected to pins 13 of commercially obtaineddiodes D of a flat-plate type by soldering 13'. Further, the electrodeleads 2 extend at right angles to the plane of the drawing sheet of FIG.11. Also in FIG. 11, the reference symbol b denotes a backing-up sheetof, for example, polyurethane, which is applied to provide a flatsurface, compensating for irregularities formed by diodes on thebackside of the contact sensor 1.

Then, as best seen from FIG. 10, on the electrodes Eo and Ep, asheet-type pressure sensitive conductive rubber 3 is placed, on whichsuperposed is a touch or contact member (surface forming member) 14which may be referred to as a skin. This surface forming member 14comprises a sheet formed by laminating on a fabric a soft foamed sheetcapable of closely contacting an object to be handled, and under thissurface forming member 14, an upper-side conductive film 16 is furtherdisposed. The electrodes Eij (pairs of Eo and Ep) are provided, whereina number of 4096 electrodes is provided within an area of about 32 cm×32cm in a square net-work or a chessboard arrangement.

Now, referring to FIGS. 12 and 13, a description will be provided of theoutput circuits for outputting the data on touch or contact from theabove described tactile sensing circuits.

FIG. 12 shows output circuits in or of a touch sensing system, whichwere made with use of CMOS-IC for the output switches and which areapplicable to the tacticle sensor shown in FIGS. 6 and 7 and the tactilesensor shown in FIGS. 9, 10 and 11. Further, FIGS. 12 and 13 illustratethe instance in which 64 electrodes Eij are used in each of the verticaland transverse directions (4096 electrodes in total).

For the multiplexor shown at 18, for operating 64 output switches Sicomprising FETS shown in FIGS. 12 and 13, use was made of a high signaloutput CMOS-IC, type 74HC238 (a surface mounting device, a product ofNEC Corporation; this same description is applicable also to the belowappearing CMOS-IC's.) as M₁ to M₈, and for the multiplexor shown by 20for operating feed-side switches Sj, use was made as N₁ to N₈ of a lowsiganl output CMOS-IC's, type 74HC 138. In each of the CMOS-IC's, theelements comprise a 3-to-8 decoder, decoding one of 8 output lines underthe condition of 3 selection inputs and 3 enabling inputs.

Thus, in order to operate 64 switches Si and 64 switches Sj, it isnecessary to use 8 each of 74HC138 and 74HC 238. Therefore, for decodersfor controlling 8 IC's, 74HC138, M₉ and M₁₀, were used for themultiplexors 20 and 18, respectively. Further, for the feed switches Sjfor the illustrated embodiment, widely used digital transistors (DTB)were used.

In the circuit Ci for operating the output switches Si in the touchsensor 1, the No. i output pin of the 64 pins in the multiplexor 18 andthe gate of FET of the switch Si were connected together by a capacitorC, and as shown in FIGS. 12 and 13, a bias voltage of -3 V was impressedthrough a voltage divider circuit comprising resistances R₂ and R₃.

For the operation of the switch Si, it is sufficient only if a voltagecapacity enough to produce a switching level for the FET is providedtherefore, the voltage (-3 V) to be impressed to the gate of FET wasobtained from a 5-V power source for operating the tactile sensor 1.That is to say, by a voltage of 5 V supplied from the 24th and 25th pinsof output terminals of a control device (not shown), an RC oscillationcircuit was excited, and the negative voltage of the alternating voltagethus obtained was supplied through a constant-voltage circuit 22 forobtaining -3 V, composed of a transistor and a constant-voltage diode.

One of the characteristics of the sensing circuit of the presentembodiment resides in that all of the required power, including the biasvoltage of -3 V for operating the gate of FET, can be supplied by asingle power source as described above.

The above described embodiment operates as follows. From the 11th to16th pins and the 19th pin (for enabling input) of the terminal 22 ofthe control device, address signals for operating feed switches Sj aresent to the feed multiplexor 20 for the electrodes Eij. Also, from the1st to 6th pins and the 9th pin (for enabling input), address signalsfor operating output switches Si are sent to the output multiplexor 18.The respective signals are modified to operation signals throughreceiver circuits 24 and 26 and then transmitted to A to C pins ofrespective decoders M₁ to M₈ and N₁ to N₈, and signals for operating thedecoders M₁ to M₈ and N₁ to N₈ are imparted to A to C pins of thedecoders M₉ and M₁₀.

Decoders M₉ and M₁₀ issue signals for operating one of decoders M₁ to M₉and N₁ to N₉, successively. To these decoders M₁ to M₉ and N₁ to N₉, andfrom the decoder M₁ . . . or M₈ or the decoder N₁ . . . or N₈ that isput into operation by the above signals, high signals are outputted foropening switches Sj and Si to be successively operated, whereby avoltage is impressed successively to the electrodes Eij, whereupon thecurrent corresponding to the degree of compression force is taken outfrom the output terminal 28.

The output switches Si according to the present invention may comprisethe switching circuits Sij shown in FIG. 2, in place of the driving oroperating circuit shown in FIG. 12. In the following, a description willbe entered into the characteristics of the switching circuit Si shown inFIG. 12, in comparison to the conventional switching circuit Sij.

When an FET is used for the output switch element, the switchingoperation of gates in the case of FIG. 2 relies upon the H of the opencollector of TTL, and it is further necessary to lower the impedance ofthe gates, so that it is required to effect a pulling up by theresistance R₁ (for example, 1 kΩ). In this case, the length of time foroutputting high signals because opening a gate is 1/64 of a total lengthof time (for there are 64 electrode leads i), and the output is L forthe remaining 63/64 length of time, whereby a power of, for example, onthe order of 10 mA flows to the resistance of 1 kΩ. A same situation asthe above applies to the remaining 63 electrode leads, and as a whole, apower of 640 mA will flow in total, whereby a considerable heatgeneration takes place.

In contrast to the above, in the output switching circuit Si shown inFIG. 12, it is possible to lower the required operation current to theorder of μ amperes. Therefore, it is possible to considerably suppressthe current capacity as a whole, reduce the feed power capacity, andsuppress the heat generation, so that it is possible to miniaturize thesensor circuit.

Further, using the sensor circuit of FIG. 12, as before indicated, thecurrent capacity required for switching operation of the FETS can beextremely small, so that the bias voltage (-3 V) to be imparted to thegate of the FETS can be taken from the 5-V feed voltage for the sensorcircuit. The switching circuits used in the prior art (for example theone shown in FIG. 2) require two power sources, a +5 V power source anda -5 V power source. As opposed to this, the circuit of FIG. 12 ischaracterized further in that it can lower the power consumption andsimplify the circuit only with the need of a single power source, sothat it becomes possible to provide a compact device.

Advantages brought about because of the sensor circuit of the abovedescribed embodiment may be summarized as follows. The 4096 outputswitches required in the prior art could be reduced only to 64; thesensor circuit could be operated only with a 5V-power source alone;therefore, the required number of parts could be reduced and it becamepossible to simplify the circuit; the current value flowing through theoutput switching circuits could be reduced; and a tactile sensing partand sensor circuits could be mounted on a single sensor board, wherebyit was possible to effect a reduction in size and weight and an increasein strength of the device.

As can be perceived from the foregoing description, in the tactilesensor 1 according to the present embodiment, 64 electrodes Eo and 64electrodes Ep are parallel connected on each of 64 leads 2 and 64 leads4 respectively. According to this arrangement, it is possible to reducethe 4096 high-speed switching elements required in the prior art to only128, whereby it is possible to lower the production cost and simplifythe arrangement of circuits around the sensing part.

Image Display System

Now, a description will be given to the image display system accordingto the present invention, with reference to an embodiment thereof asillustrated in FIG. 14. It is possible to arrange such a system so thatsignals of the detected compression force (touch) at each of the sensingpoints in the distribution type tactile sensor or a tactile image sensor1 according to the present invention are sent to an imaging unit 30 andtherein converted to imaging signals, which are inputted through animage input device 32 to a personal computer 34, in which the signalsare subjected to a prescribed processing. According to this system, itis possible to display the tactile detected detail of an object sensedby the tactile image sensor 1 in the form of an image on an imagedisplay unit 36, in which two monitors, comprising a monochrome (blackand white) television tube and an RGB three-primary-color televisiontube, are used in the illustrated embodiment.

The image input device 32 used in the present embodiment had apseudo-color-through function for displaying the input image wherein theimage shape is changed with the lapse of time, comprising a 64-levelgradient tone display function and a 4 stationary image displayfunction. For the personal computer 34, use was made of a 640 KBNEC-PC9801 machine equipped with software providing main menus whichenable image freezing, pseudo-colouring, image processing,enlargement/reduction, inter-image processing, histogram processing,image saving/loading, and so on.

Next, with reference to the block diagram of FIG. 15, a description willbe given of an example of the imaging unit 30. FIG. 15 represents thesystem in which the plane shape of an object against which the tactilesensor 1 is contacted is displayed intact on the display device 36.

In the system illustrated in FIG. 15, the tactile sensor 1 is operatedby the imaging unit 30 to scan respective electrode leads 2 and 4, and avoltage is applied successively to electrodes at the sensing points. Thecontrol in this respect is made as follows. Pulsed signals, which aregenerated from a synchronous signalling circuit 37 on the (vertical)side of the leads 2 and a synchronous signalling circuit 38 on the(horizontal) side of the leads 4, are subjected to a timing regulationby timing controllers 39 and 40 and are then sent to multiplexors 18 and20 through counters 41 and 42, and decoders 43 and 44, whereby electrodeleads 2 and 4 are scanned and switches (not shown) are successivelyoperated to impress a voltage for sensing the resistance at respectivesensing points. In the above, current is supplied from the multiplexor18 to a contact signal divider circuit 45, in which the signalscorresponding to the tactile detection (compression force) are selectedout, and the signals are then sent to a synchronized mixer 48 through areturn back period holding circuit 46 and a selection circuit 47. Then,the signals of touch-detected forces are amplified by a video-amplifier49 synchronized with the image display device, then sent to the imageinput device 32. After the signals have been processed by the personalcomputer 34 according to a selected one of the above-described mainmenus depending on a command preparatively inputted from an input device50, they are displayed on the display device 36.

Applications of the above-described image display system of the presentembodiment include research and studies in medical fields and in thefields of the human-factors engineering, such as studies on thesplayfoot, of which it is said that today more children suffer from thisthan ever before. In addition, studies and research on comfortablechairs, studies on decubitus suffered by aged people long in bed, and soforth, are possible. Also, in the field of education, the system can beeffectively utilized, for example, in replacing the conventionallyoperated hand-to-hand guidance or education of such techniques aspalpation, massaging, and so forth, with ones utilizing pictures andnumerical values.

The tactile image sensor 1 in the above-described embodiment canconsiderably reduce the number of high-speed switching elements, so thatit becomes possible to process data from a tactile image sensor having anumber of sensing points for a high-speed image processing by a personalcomputer, whereby it is possible to considerably curtail the cost of thesystem. For example, a conventional system utilizing a mammoth computercosting at least 10 million Japanese Yen can be modified to a morewidely utilizable system of a drastically reduced cost.

Further, by using a personal computer in the above system, changing ofprograms can be easily made, so that the system can have a highversatility, capable of meeting a variety of demands, even though thehigh-speed performance may indispensably be sacrificed depending onparticular demands.

FIG. 16 illustrates the operation of the above image display system.When the palm 53 of a hand is pressed against the tactile image sensor1, according to the above-described operation processes the compressionforce (touch) at respective sensing points is detected, processed anddisplayed as an image of the palm 53 on the display device 36 (in FIG.16, the above-described devices and units 30 to 34 are shown incollection as an image processing device 52). The display can optionallyenploy any one of various manners of displaying such as a real timedisplaying, displaying as a stationary picture, displaying in contrastof brightness and darkness, displaying in gradient brightness or colortones corresponding to the strength of forces with which the contour orrespective portions of the palm is pressed, displaying in the form of acontours diagram, and displaying as a histogram of compression forces ona diagram of the sensing points.

Now, with reference to FIG. 17, a description will be given of theessential points of a control system in the instance in which thedistribution type tactile sensor according to the present invention isapplied to control the holding power of a robot's hand. The tactilesensor used in the present embodiment comprises an 8×8 matrixarrangement, which was used for sensing contact pressure, and feedswitches and output switches (8 switches on each of the feed side andthe output side) were each adapted to an analog control. In FIG. 17, therobot's hand shown by 55 is controlled by a control device 56 based ondetected signals from the tactile sensor 1. The control device 56 wascomposed of a one-chip microcomputer 57, an input/output device 58, anA/D converter 59 for converting current signals corresponding to contactpressures into digital values, and a D/A converter 60 for convertingsignals for controlling the holding power of the robot's hand 55 intoanalog signals.

The above described distribution type tactile sensor according to thepresent invention can be effectively applied as means for controllingcontact pressure, having a simple structure and yet exhibiting a highcontrol accuracy, in the cases of controlling, for example, the holdingor grasping power of robots.

Now, with reference to FIG. 18, a description will be given of thestructure of a plate type sensor which is suited to receive a humancandidate thereon and is chiefly suitable for detecting an image of asole or soles of the feet of a human candidate contacting the sensor.The electrode used in the present embodiment had a pattern of a swastikashape as shown in FIG. 19, even though it is similarly effective if useis made of an electrode of a comb-type shape as shown in FIG. 3.

FIG. 18 is a partly broken-away perspective view, showing a touch sensor1 with a portion thereof cut away. As shown, the tactile sensor 1comprises a printed circuit plate 17 provided with electrodes Eij formedby printing electrodes and electrode leads integrally and in a belt-likeform plies of belts of a pressure sensitive conductive rubber 3, formedin belts similarly to the electrodes Eij, are provided on which a cover62 (0.5 mm thick) made of a urethane rubber is applied. On the uppersurface of the cover 62, a (tactile or touch) surface forming member 14of a high quality paper printed with the prescribed pattern on the uppersurface thereof is applied, in which the peripheral edges of the surfaceforming member 14 and the cover 62 are appropriately fixed. Betweenadjacent belts of the pressure sensitive conductive rubber 3, aseparator is further arranged.

In the printed circuit plate 17, the swastika-shaped electrode Ep (FIG.19) is formed in a central region thereof with a conductive through-holeh, to which there is connected by soldering a mini-mold member 64 havingdiodes D capsulated two each therein, for preventing the generation ofstray currents, and to which also connected are electronic parts such asIC's (not shown) and diodes required for the printed wiring (not shown).The electrode Ep (FIG. 19) comprises a belt-like structure having a holeformed therein by the removal of an electrode Eo. Further, in FIG. 18,an illustration of the swastika-shaped electrodes is not shown.

Between adjacent mini-mold members 64, backing-up members b comprising abelt-like urethane material and having a thickness (2 mm thick) greaterthan that of the mini-mold members are disposed, and under thebacking-up members b, there is disposed a sandwich structural body 65comprising an an integrally formed aluminium honeycomb structural body.The sandwich structural body 65 comprises a honeycomb member 67sandwiched between a pair of reinforcing plates 66, and this structuralbody 65 is adapted for placement on a floor (not shown).

The sandwich structural body 65 can be manufactured to be relativelythin and yet highly strong with a simple structure, and by using it, itis possible to provide a sensor which can stand a high concentration ofload, for example 300 kg.

By making the pressure sensitive conductive, rubber 3 in the form ofbelts and by arranging separators between adjacent belts of the rubber 3as above, it is possible to suppress the extent of deformation ordisplacement of the contact surface which is likely due to forces to beproduced in lateral directions when a human candidate gets on or downfrom the contact surface. Also, the tactile or touch surface formingmember 14 and the cover 62 thereunder serve to prevent forces acting inthe lateral directions from easily being transferred to the respectivemembers under them.

Then, with reference to FIGS. 20, 21 and 22, a description will next begiven to a distribution type tactile sensor adapted to applications ofcurved surfaces, and also of the manners of use thereof.

As shown, unit sensors 1o comprise a pressure sensitive conductiverubber 3 and electrodes Eo and Ep, and respective unit sensors 1o areconnected together by output-side electrode leads 2 and feed-sideelectrode leads 4 to provide tactile pressure sensing circuits. Thefeed-side electrode leads 4 of each unit sensor 1o are connected to amultiplexor 20, while the output side electrode leads 2 are connected toa multiplexor 18.

Respective electrode leads 4 are successively connected to a powersource (+B) by switches comprising a transistor Tr, which undergoeson-off operations responsive to signals from the multiplexor 20.Respective electrode leads 2 are successively connected to an outputline O.P. by switches comprising FETs which undergo on-off operationsresponsive to signals from the multiplexor 18. Therefore, by scanningthe electrode leads 2 and 4, it is possible to successively sense theresistance of each unit sensor 1o through the single output line O. P.

FIG. 21 is a perspective view, showing the unit sensor 1o of FIG. 20with a portion thereof broken away, in which the electrode Ep connectedto electrode leads 4 comprises a printed electrode on a substrate plate17, on which a pressure sensitive conductive rubber 3 is disposed, andon which the other electrode Eo is laminated. The periphery of this unitsensor is wholly encased in a cover 62 of a sealing material such as amodified urethane rubber. Thus, in the present embodiment, thefront-side face of the electrode Eo is arranged on the side of thepressure bearing surface (touch surface) 14.

Under the substrate plate 17, terminals 72 and 73 are disposed, which donot conduct to each other. The terminal 72 is connected to the electrodeEp through a conductor 74 filled in a through-hole h in the substrateplate 17, and a diode D is connected to the conductor 74. The terminal73 is connected to the electrode Eo through a conductor 75. Thus, theelectrode Ep should be connected to a power source so that, through thediode D, it comprises a positive polarity.

Terminals 72 and 73 on the one hand and electrode leads 2 and 4 on theother hand can be connected to each other by any of such as soldering, aplug-socket arrangement and staking or calking. Further, in FIG. 21, thereference numeral 76 denotes an adhesive sheet with which the unitsensor 1o may be attached to an object to be sensed.

FIG. 22 shows a perspective view, illustrative of a manner ofapplication of the curved surface tactile sensor 1 of the presentembodiment, which is applied to a chair. As shown, a plurality of theunit sensors 1o shown in FIG. 21 are set in a chessboard arrangement onthe back cushion 79 of the chair 78, forming a curved surface, and eachof the electrode leads 2 and 4 is connected to a terminal box 80 housingmultiplexors 18 and 20, as shown in FIG. 20, therein. Tactile pressuresignals are displayed in terms of numerical data or contours on adisplay device 36 through an imaging unit 30. According to the describedsystem, it is possible to determine the relationship between theconfiguration of the chair and the physical construction and/or theposture of a user of the chair in terms of dynamic characteristic data.

In FIGS. 23 and 24, respective electrode leads 4 and 5 are fixed in azigzag arrangement to a stretchable ribbon-type member 20, whereby theease of handling of the tactile sensor 1, shown in FIG. 20, isincreased. As the distance between adjacent unit sensors 1o which arearranged in a relatively large spacing is increased, the electrode leads2 and 4 undergo stretching together with the ribbon-type member 20. Whena sensing operation is over and the pressure application is thenremoved, the ribbon-type member 20 can return to its original condition,so that the electrode leads 2 and 4 can be prevented from undergoingtangling and the handling of the touch sensor can be facilitated.

FIGS. 25 and 26 show respectively in a perspective view a unit sensor 1ofor attaching to a robot's hand, which comprises mutually separatesensor parts 84 and connector parts 85, of which the sensor part 84 isexchangeable. Unit sensors 1o are connected to one another by amechanical liking member so that the sensor part 84 can be preventedfrom undergoing an excessive force application. In the condition inwhich the sensor part 84 and the connector part 85 are togetherassembled, the size of the unit sensor 1o is approximately 5×5×5 (mm).

Electrodes Ep and Eo comprise the so-called comb-shaped electrodesformed by print wiring, and in the gap g between the electrodes Ep andEo, an insulating material is filled to prevent short circuiting fromoccurring. On the electrodes Ep and Eo, there is applied a pressuresensitive conductive rubber layer 3' formed by coating a pressuresensitive conductive coating material, on which a conductive layer 16'formed by a conductive coating material is further provided. On theunderside of the sensor part 84, there are provided a conductor pin 86to be connected to a diode D, a conductor pin 87 to be connected to theelectrode Eo through a conductor 74, and two pins 88 merely consistingof a mechanical connection member (one of the two pins does not appearin FIG. 25). By the four pins 86, 87, 88 and 88, the sensor part 84 isfixed to the connector part 85.

The connector part 85, which is made of a resin, is provided withsockets 86', 87' and 88' (two) into which the above pins are inserted,of which the socket 86' is connected through a conductor 74 to aterminal 72 joined to a connector pin 90 provided to the electrode lead4, whereby the electrode Ep and the electrode lead 4 are connected toeach other. The above described four pins 86, 87, 88 and 88 mechanicallyand detachably connect the sensor part 84 and the connector part 85 toeach other. Further, the reference numeral 91 denotes conductorsconnecting terminals 72 and 72 together and terminals 73 and 73together.

A plurality of connector parts 85 (the illustration is limited to onlyone) are vertically and laterally arranged by connecting cords orstrings 93 applied through through-bores 92 to altogether form thesensing part of the curved surface tactile sensor shown in FIG. 20. Theunit sensor 1o shown in FIGS. 25 and 26 is suitable for attachment to anon-plane portion of a robot's hand, for gripping an object therewith.

With reference to FIG. 27 and FIG. 28, a sectional view taken on lineIIXXX--IIXXX of FIG. 27, a description will be given to another modifiedexample of the embodiment shown in FIG. 21. The unit sensor 1o of thepresent embodiment comprises an electrode Ep (or Eo) attached on oneside surface of a spacer 95 comprising an insulator formed with athrough-hole for fitting a pressure sensitive conductive rubber 3therein and a pressure bearing plate 96 comprising, for example, a resinplate, attached to the pressue sensitive conductive rubber 3, on theouter side of the electrode Ep (or Eo).

For the flexible electrodes Eo and Ep and the electrode lead 2 (or 4),use may be made of any of products prepared by etching a flexiblecircuit substrate plate, and products prepared by printing patterns ofelectrodes and electrode leads on a flexible film such as polyesterfilms. Preferably, surfaces with the electrodes Eo and Ep should betreated with a material such as gold plating and treated with carbon inorder to prevent a contact resistance from being generated.

As shown in FIG. 28, in the present embodiment electrodes Eo and Ep andthe electrode lead 2 are formed by etching the conductive layer on asingle flexible printed circuit board 17, which is folded in two with aspacer 95 interposed therebetween, to provide electrodes of a sandwichstructure. The pressure bearing plate 96 can accurately transmit thepressure applied thereon to the pressure sensitive conductive rubber 3,and in the illustrated embodiment, it has a diameter appreciably smallerthan that of the pressure sensitive conductive rubber 3. This pressurebearing structure can be provided in any of appropriately modifiedmanners. For example, as an alternative means for providing a pressurebearing member, it is envisaged to dispose a small plate piece having afurther smaller diameter than the above plate 96 in the vicinity of thecenter of the rubber 3, and place a flexible pressure bearing sheet onthe plate piece so that the pressure applied on the pressure bearingsheet can be transmitted, at a central region of the sheet, to thepressure sensitive conductive rubber.

As shown in FIG. 27, the diode D for preventing a stray current fromflowing is connected at its one end to an extended elongate portion ofthe electrode Eo and soldered at its other end on the electrode lead 4formed on the flexible printed circuit board 17. A portion of theprinted circuit board 17 removed of the conductive layer is contactedwith the flexible printed circuit board 17 on the side of the electrodeEo, and on the surface thereof, similar pressure bearing plate as theabove plate 96 is attached. The tactile sensor 1 for curved surfacesshown in FIGS. 27 and 28 is simple in structure and easy to produce andhandle, and was found to possess a remarkable sensing performance.

With reference to FIG. 29 to FIG. 32, a description will next be enteredinto the instance of applications of the present invention in which thetactile sensor according to the invention is utilized in order to obtaindata for designing shoes. The tactile sensor 1 of the present embodimentconsists of a flexible sensor formed of a rubber for a shoe sole andcomprises a heel-part sensor 99 and a sole- or front-part sensor 100,attached to the sole of a shoe 98.

As shown in FIG. 30, the unit sensor 1o used in or for the sensors 99and 100 is composed of electrodes Eo and Ep parallel arranged on, forexample, a printed circuit board 17. Leading wires 101 and 101 areapplied through through-holes h in the circuit board 17, and connectedto electrodes Eo and Ep by soldering and extended beyond a backside sideor underside surface of the circuit board 17. A pressure sensitiveconductive rubber 3 is placed on the electrodes, and a conductive film16 is disposed on the rubber 3 opposite the electrodes Eo and Ep.

A multiplicity of unit sensors 1o is sealably embeded sensor by sensorin a rubbery block 102 having a convex contour. By way of an example,the blocks are of a size of about 6 mm in length in a longitudinaldirection and about 8 mm in length in a lateral direction, and the unitsensors 1o have a size of about 3 mm×6 mm. In the illustratedembodiment, the electrodes Eo and Ep comprise parallel arrangedrectangular electrodes, but they may comprise electrodes of any othershape, for example a comb-type shape.

The convex block 102 is provided with a recess 103 in which a unitsensor 1o is placed and sealed with a filling material 104 comprisingfor example a rubber, in the condition in which the lead wires 101 areexternally projected. As shown, the pressure bearing part in the recess103, indicated at 105, is structured to have an increased thickness incomparison to the peripheral part of the block 102 so that a loadapplied can be concentrated on the unit sensor 1o. In FIG. 29, theblocks 102 are disposed in a line arrangement in the lateral direction,and in the longitudinal or back and forth direction there are providedgrooves 108 in which to place diodes D for preventing stray currentgeneration, the diodes D being disposed over a whole of the heel-partsensor 99 and the front-part sensor 100.

Blocks 102 shown in FIG. 29 are individually fabricated as shown in FIG.32 and are bonded on a substrate board which is not shown, in anarrangement such that, as shown in FIG. 31, while they lie close to oneanother in the lateral direction, they are spaced from one another bygrooves 108 in the back and forth direction. As an alternative means tothis, it is also possible to integrally form the blocks 102 and thegrooves 108, and after the unit sensors 1o are sealed as stated above,to attach the resulting product by bonding onto a substrate comprising ashoe sole material, such as a rubber, which is not shown.

Electrode leads 2 and 4 shown by broken lines in FIG. 31 are connectedto the lead wires 101 from the blocks 102 so as to form the sensingcircuit shown in FIG. 20. Further, whereas the diodes D may be arrangedeither on the side of the electrodes Eo or that of the electrodes Ep, aslong as they are connected in a correct direction electricially in theillustrated embodiment, they are provided on the side of the electrodeEo. After connection of respective wires is finished, the heel-partsensor 99 and the front-part sensor 100 are attached to the sole of theshoe 98. Further, the reference numeral 107 in FIG. 29 denotes wireharnesses comprising the electrode leads 2 and 4.

The tactile sensor 1 shown in FIG. 29 differs from each of thepreviously described tactile sensors 1 in that the number of electrodesattached to the electrode leads 2 and 4 is not constant but is locallyvaried. Thus, in the tactile sensor 1 according to the presentinvention, it is not always necessary that electrodes are provided in achessboard arrangment or that spacing of the electrodes is constant.

Now, with reference given to FIGS. 33 and 34, a description will be madeof an adaptor which makes it possible to suitably change the touchdensity.

FIG. 33 shows an adaptor 110, which is composed of a plurality of pins111 and a pin holder 112. Each pin 111 has a sensing end 113 for contactwith an object and a touch transmission end 114 provided with a pressurepiece for pressing against a tactile sensor 1. The pin 111 isintermediately provided with a spring 115 so that the sensing end 113can undergo motion of a stroke greater than a deformation stroke of apressure sensitive conductive rubber 3. In the present embodiment, inorder to facilitate smooth transmission of force, use was made of such adevice in which the pin 111 was inserted through a tubular guide 116made of for example a soft spring. The guide 116 is effectively usefulalso in the cases in which the pin 111 is provided in a curvedcondition. Also, means can be taken for example to apply a cap of asynthetic resin to the sensing end 113 of the pin 111 so that this end113 can contact an object softly.

The pin holder 112 comprises a plate-type holding part 117 on the sideof the sensing end 113 and a plate-type holding part 117 on the side ofa tactile sensor 1, holding the pins 111 and guide 116 in postion. Oneof the holding parts 117 is provided with bores 118 for passing pins 111therethrough, so as to provide points at which the sensing ends 113 ofthe pins 111 are to be matrix arranged. The other of the holding partsis provided with bores 119 also for pins 111, so as to locate the touchtransmission ends 114 on the prescribed points on the tactile sensor 1.Stoppers 120 are appropriately provided so as not to allow the pins 11to come out of the holder 112.

Lead wires 121 connected to touch transmission ends 114 are electricallyconnected to pins 111 through wrapping parts 122 made by coiling alinear elastic body so that they can function also as a member biasingthe pins 111 outwardly.

Although this arrangement is not shown, the pin holder 112 is fitted inthe prescribed position in the tactile sensor 1 and fixed by screws. Asa matter of course, it is possible to detachably secure the pin holder112 to the sensor 1 by any other suitable means. Therefore, by providinga variety of pin holders 112 having different sensing or analyticcapacities, it is possible to enhance the versatility of the tactilesensor 1. Further, if the provisions of bores 118 and 119 are reversedin comparison to the above arrangement, then it is possible to broadenthe sensing area for each sensing operation.

In the arrangement shown in FIG. 33, directions in which pins 111 extendare at an inclination relative to one another, so that a problem islikely that as pins 111 are pressed in and out, distances among sensingends 113 undergo changes. To avoid this problem and to maintaindistances among the pins 111 constant, it is possible to make the bores118 in the holding parts 117 have a relatively great length, to providean additional holding plate 117 having bores 118 in a same positionalarrangement as in the other holding plate 117 and/or to arrange the pins111 in a parallel disposition on the side of the sensing ends 113. Bymaking a same arrangement as above also on the side of the touchtransmission ends 114, it is possible to ensure that forces are appliedat right angles to the tactile sensor 1.

FIG. 34 is a view, taken for illustration of another embodimentrepresenting the instance in which concave and convex irregularities onthe bottom in a relatively small hole or cavity are detected, and itshows an operation condition in which a concave or convex portion 125 atthe bottom of a hole 124 shown in a sectional view is detected by pins111. In the adaptor 110 shown partly broken away, pins 111 are held byholding parts 117 and 123 and also by a plurality of intermediateholding parts 126, provided in a pin holder 112, in an arrangement suchthat distances among the pins 111 required at the side of the touchtransmission ends 114 are narrowed compared to distances required at theside of the sensing ends 113.

FIG. 34 shows the condition in which the sensing ends 113 are inabutment against the concave and convex portion 125 at the bottom of thehole 124, and wherein tactile contact by the sensing ends 113 istransmitted to electrodes. Further, although this is not shown in FIG.34, in a same manner as in FIG. 33, pins 111 are provided with springs115, stoppers 120, lead wires 121 and wrapping parts 122, so thatconcave and convex surface conditions in small or narrow holes can bedetected. Also, if the pin holder 112 of the present embodiment is madecapable of being bent, it becomes possible to detect concaves andconvexes which are externally invisible.

In the field of electronic appliances, lately it has been increasinglydemanded that a reduction in size should be incessantly realized, and tocope with the demand, it is urged to increasingly effect a densificationof the wiring to be printed on a printed circuit board, to increasinglyminiaturize various parts such as chips to be mounted on the printedcircuit board and to reduce the interpart spacing.

In connection with the above, it is required to perform inspections orexaminations to determine whether the wiring is free of errors, one ofwhich is an inspection or examination for determining if the prescribedparts are provided at their prescribed locations. Now that variousminute parts and elements are arranged in a close relative arrangement,it is difficult to perform the above required inspection visually orwith an eye, so that today the inspection is operated by pressing theprinted circuit board against a board provided with a number of pins fordetecting convex and concave surfaces thereof by a tactile sensor. Usingthe adapter described above with reference to FIG. 33 and outputting theresult of detection in the form of the prescribed image on a displaydevice such as CRT, it is possible to enhance the accuracy and theoperation efficiency of the inspection.

In the embodiments shown in FIGS. 33 and 34, the touch transmission ends114 are formed as electrodes of one of the two polarities, but italternatively is possible to provide electrodes separate from the touchtransmission ends, and to let these pin ends 114 function only as meansfor transmitting the touch or the tactile data.

As described above, the distribution type tactile sensor according tothe present invention brings about the following effects or results.

(1) Now that the number of sensing points can be increased so as tocorrespond to the product of the number of electrode leads of groups ofelecrodes of a polarity multiplied by the number of electrode leads ofgroups of electrodes of another polarity, it can becomes possible tosimplify the arrangement of the tactile sensing control circuits,enhance the sensing speed, and realize a real time display of imagesrequiring a number of tactile sensing points. Also, the number ofrequired parts can be reduced, and the tactile sensor can be mounted ona surface of a sensor board with electrodes of a tactile sensingcircuit.

(2) Now that it is possible to prevent otherwise likely stray currents,touch can be detected at a high accuracy.

(3) Now that the tactile sensor can be mounted on a sensor board with atactile sensing circuit as above, the supporting of the sensor isfacilitated, and it is possible to reduce the thickness of the sensorand to provide a sensor for a large load application.

(4) The tactile sensing circuit structure can be simplified as above, sothat it is possible to make a sensor having unit sensors assembled in atwo-dimensional arrangement and connected to one another with flexibleelectrode leads, whereby it is possible to provide a sensor for curvedsurfaces applicable to any optional curved surfaces.

(5) Although the size of a tactile sensing part is limited by the sizeof electrodes, an adapter is provided, which may be attached to thesensor to reduce the unit area required for tactile sensing.

(6) As a result of the above, it is now possible to apply the tactilesensor in a wide range of technical areas such as for studies on and/orfor collections of data for designing in the field of human-factorsengineering, for medical studies in the field of rehabilitation ofhandicapped people, and for industrial utility such as for or in robot'shands.

What is claimed is:
 1. A distribution type tactile sensor comprising:aplurality of electrodes provided in pairs at respective pressure sensingpoints on a pressure sensitive conductive rubber sheet capable ofchanging the electrical resistance responsive to compressive forces; andrectifier means provided to respective electrodes for rectifying thecurrent flowing across each pair of electrodes through the rubber sheet,the electrodes being divided into groups each comprising electrodesarranged in a line corresponding to respective polarities of theelectrodes, wherein electrodes in respective electrode groups areparallel connected to one another through electrode leads, anddirections of a division of electrode groups divided into respectivepolarities are crossed with one another at respective pressure sensingpoints; wherein belts of the pressure sensitive conductive rubber sheetare disposed in a mutually parallel and spaced arrangement on pairs ofelectrodes provided on a sensor board in a chessboard arrangement, acover having a relatively low friction resistance and comprising aflexible material is applied to the surfaces of the belts of the rubbersheet, and a flexible surface-forming member is further applied on thecover thereby providing a laminate structure; and wherein the peripheraledge of the laminate structure is fixed and electrodes having respectivepolarities are divided into respective groups in a mutuallyperpendicular arrangement.
 2. The tactile sensor as claimed in claim 1,wherein each pair of electrodes is provided in a close arrangement toeach other with a prescribed space therebetween, on one side surface ofthe pressure sensitive conductive rubber sheet.
 3. The tactile sensor asclaimed in claim 1, wherein each pair of electrodes is provided in amutually facing arrangement, one on a front side surface and the otheron a backside surface of the pressure sensitive conductive rubber sheet.4. The tactile sensor as claimed in claim 1, 2 or 3, wherein a feedswitch comprising switching elements is provided to respective electrodeleads and to respective electrode groups of one polarity, while anoutput switch comprising switching elements is provided to respectiveelectrode leads and to respective electrode groups of another polarity.5. The tactile sensor as claimed in claim 1, 2 or 3 wherein a pluralityof electrodes of one polarity which are provided in pairs through thepressure sensitive conductive rubber sheet and distributed in pairs, onthe one hand, and a plurality of electrodes of another polarity whichare provided in pairs through the rubber sheet and distributed in pairs,on the other hand, are respectively divided into groups in a mutuallycrossing arrangement, electrodes of a same group being connected to oneanother by an electrode lead, and wherein an imaging unit is providedfor connecting a power source successively to the groups of electrodesof one polarity, taking a signal current successively from the groups ofelectrodes of another polarity and imaging the signal currents, and adisplay means is provided for displaying the data on the compressionforce acting at respective pressure sensing points, in the form of animage based on the result of the imaging.
 6. The tactile sensor asclaimed in claim 1, 2 or 3 wherein a plurality of unit sensors providedwith electrodes arranged in pairs through the pressure sensitiveconductive rubber sheet is provided in a two-dimensional arrangement,the electrodes of respective polarities being divided into mutuallycrossing respective groups, electrodes of a same polarity in a samegroup being connected to one another through an electrode lead, eachadjacent unit sensors being connected to each other with a spacetherebetween, the space between adjacent unit sensors being variable. 7.The tactile sensor as claimed in claim 1, 2 or 3 which is provided withan adapter comprising pins having a concave and convex detecting end tobe contacted against an object and an opposite touch transmission end,the detecting ends being arranged at prescribed positions, the touchtransmission ends being arranged so as to transmit compression forces topoints on the pressure sensitive conductive rubber sheet at which pairsof electrodes are provided, said adapter further comprising a pinholder.
 8. The tactile sensor as claimed in claim 1, wherein anelectronic member to be provided to respective electrodes and a wiringare provided on a backside of the sensor board, and under the electronicmember and the wiring, a support member is provided, which comprises acomposite material of a sandwich structure provided with asurface-forming member on each side surface.